Thermal relay



Oct. 14 |924.

F. H. MILLER 'THERMAL RELAY Filed June 9, 1920 y mvENToR Frederik/c ////er WITNESSES:

ATTRNEY Patented Oct. 14, 1924.

UNITED vSTATES PATENT OFFICE.

FREDERICK H. MILLER, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

THERMAL RELAY.

Application led .Tune 9,

T o all w hom it may concern:

Be it known that I, FREDERICK I-I. MILLER,

a citizen of the United States, and a resident of lVilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvementr in Thermal Relays, of which the following is a specification. Y My invention relates to electrical protective devices and particularly to thermal relays.

One object of my invention is to provide a thermal relay that shall have sutlicient time interval in the operation thereof to effeet protection of electrical apparatus against overloads.

Another object of my invention is to provide a relay comprising a thermal-respon sive element and means for transmitting heat thereto, other than the natural inherent heat of the element, to actuate the latter in response to a current of predetermined value therein.

A further object of my invention is to provide a relay, of the above indicated character, that shall be adapted to be used in ordinary cartridge-type fuse clips, be relatively inexpensive to construct and reliable and effective in its operation.

In United States Patent No. 1,438,607, issued Dec. 12, 1922, to applicant and J. II. Procter and assigned to the Westinghouse ElectricfJ Mfg. Co., is set forth the general principles of a certain portion of the herein disclosed invention, as employed in a fuse.

In practicing my invention, I provide an enclosed cylindrical casing having connecting ferrules at the ends thereof to be re# ceived in the ordinary cartridge-type fuse clips. A bimetallic member is secured, and electrically connected, at one end to one of the errules and extends longitudinally in the casing to a position adjacent to the other end of the casing Where it is connected, by a flexible conductor, to the other end fer'- rule. A contact member at the free end of the element coacts with a stationary contact member that is insulated from the cartridge terminals and is connected to an auxiliary circuit. y

To secure additional hea-t for the element, other than the natural inherent heat thereof, when included in an electrical circuit, I pro- 1920. Serial No. 387,591.

vide one or more magnetizable rings or memf bers that are mounted on the element. These rings are heated by hysteresis and eddycurrents, caused by alternating or fluctuating direct current in `the element, and this heat is conducted from the rings to the element to augment the natural heat thereof.

Figure 1 of the accompanying drawings is a longitudinal sectional view of a thermal relay embodying my invention, together with a diagram of an electric circuit with which it is adapted to co-operate; Fig. 2 is an enlarged diagrammatic detail view of a modified form of bimetallic element embodying my invention, and Figs. 3 and 4 are de tail sectional views of modified forms of the element shown in Fig. 2.

In Fig. 1, a cylindrical casing 1 is provided with a ferrule 2 at one end and a ferrule 3 having an opening 4 therein at the other end thereof. Rivets 5 secure a bimetallic element 6 at one end to a supporting member 7 that is secured, at one end, to the ferrule 2 by a screw 8. The bimetallic member 6 comprises two members having different coefficients of expansion. A flexi ble conductor 9 connects the free end 10 of the bimetallic element 6 tothe ferrule 3. An insulating sleeve 11 supports a terminal screw 12, in the opening 4 of the ferrule 3, and a conducting supporting member 13 for a stationary contact member 14 is connected between the yscrew 12 and one end of the member 7 through an insulating member or plate 15. A resilient contact member 16, connected to the free end 1() of the element 6, is adapted to co-operate with the stationary contact member 14.

The ferrules 2 and 3 are connected to conductors 17 and 18, respectively, which are connected to a source of power (not shown), through a circuit interrupter 19, a conductor 20, and a motor or other electrical translating device 21 which it is desired to protect. f

Thus, the main circuit for the device 21 extends from the interrupter 19, through the conductor 20, the device 21, the conductor y18, the ferrule 3, the flexible conductor 9, the bimetallic Aelement 6, the member 7, the ferrule 2, and the conductor 17 to the interrupter 19.y ,V

lAn auxiliary circuit is connected to the above mentioned circuit at the contact member 16 and extends through the stationary contact member 1st, the member 13, the screw 12, a conductor 22 and a holding coil 23 of the interrupter 19 to the conductor 20.

Vith thel above described arrangement, the current passing through the bimetallic element 6 is substantially the same as lthat passing through the device 21; consequently, the heating of the element 6 is a measure of the heating of the device 21. T When employed in circuits carrying relatively great values of current, bimetallic elements simil'ar'tothe element 6, are actuated to flex according tothe Well-known principle of ditl'erent coefficients of'e'xpansion oit' the metalscomprised in the element. But, on circuits adapted for relatively l small values of current, diiiculty isl experienced in obtaining suiiicie'nt flexure of the element toactuate the contact members of a circuit.

vTo 'overcome this diiiiculty, in a simple, effective and economical manner, T'prop'ose the use 'of magnetic rings 'orban'ds 24 that are mounted von the element 6. With this arrangenient,"the element 6 constitutes substantially, the yprimary Winding oi a series transformer having a plurality of closed single-turn lsecondary windings.

Uien an alternating current or a fluctuating ldirect current traverses the element, heat is generated, by electromagnetic induction, intheringsQet to cause hysteresis and eddy-current losses. This heat is in addition to th'en'ormal heat created in the element by thecurrent and is returned or conducted to the element jto vcause the'latter to iieX more eiectively When the dangerous current value isfsmall. n l l Thus, when the temperature of the device 21 'reaches' y'a` dangerous degree, the Vcircuit of the'holding coil '23 Will be interrupted to permit the Yinterrupter19to open.' `With the lapse of time, 'during Which the device 21 and the element 6 are cooled, the latter Will return to Vits initial shape and close the circuitof the coil 23. This vvill close the interrupter 19 and the vcircuit of the device 21.

In Fig. 2, the element 6a, supported on a basepinember '25, is disposed to interrupt thel main circuity directly, through a conductor'v26, a terminal 27, the element 6, a contact portion 28, at the free end 10 of the element, and a stationary contact terminal member 29 and a conductor 30 that are supported by an insulating member 31.

As indicated in Figs. 3 and 4, respectively, the element 6b may be completely or partially covered by lagging material 32 toconserve the heat `and to Vdirect it toward the side of the element having the greater coeiiicient 'of expansion to give greater iieXure.

Whilel have shovvn and described particular forms or my invention, changes may be effected therein Without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention 1. A thermal electric relay comprising a thermal-responsive device adapted to be connected in an electric circuit and inductive means intimately thermally associated therewith for heating the same.

2. A thermal electric relay comprising a device movable by heat action and adapted to be connected in an electric circuit, and inductive heating means intimately therefor thermally associated therewith.

3. A thermal electric relay comprising a thermal-responsive device connected in a circuit and inductive means responsive to current in the circuit for augmenting the inherentheat of the thermtil-responsive device.

1. A thermal electric relay comprising a thermal-responsive device and means magnetically related to the circuit for only assistingin the heating of the thermal-responsive device.

A thermal electric relay comprising a thermal-responsive device and magnetizable means magnetically associated With the thermal-responsive device and intimately associated therewith for heating the latter.

6. The combination with a biinetallic element, of short circuited inductive means for heating the same.

,7. In an electric circuit, the combination With a bimetallic element in the circuit, oi inductive means responsive to current in the circuit for heating the element constituting closed `electrical and magnetic circuits. Y

"8. vInv an `Velectric circuit, the combination With a plurality of metal members of dif- Yerentcoeiicients ofexpansion connected in said circuit and coacting to-efect a differential movement therebetween, o1 inductive meansresponsive to current in the circuitfor heating said members. e

9. A thermal-responsive relay comprising a bimetallic element, and a magnetizable member surrounding said element and yresponsive to current therein. for heating the same.

10. A thermal-responsive relay comprising a bimetallic element, and a magnetizable member mounted on said elementand responsiveto current thereinfor heatingthe same.

11. A thermal-responsiverelay comprising a bimetallic element and a magnetizable member embracing, and secured to, the element.

12. A thermal-responsive relay comprising a bimetallic element, and aiplurality 'oi magnetizable members surrounding, and mounted on, the element.

13. A relay comprising a thermal-responsive element consisting of tWo materials having different coeiiicients of expansion and secured in face-to-face relation, and means for thermally insulating a portion of the element.

14. A thermal-responsive element comprising a plurality of members of different coefiicients of expansion arranged to preclude relative movement therebetween and means for thermally insulating one of said members.

15. A thermal relay comprising a casing, abimetallic element therein, means heated by hysteresis and eddy-current losses thermally associated with the bimetallic element, and a contact member controlled by the bimetallic element.

16. A thermal relay for an electric circuit containing a translating apparatus, comprising a thermally-responsive element heated by the circuit current, and magnetic means secured to the thermal element and movable therewith, said means co-operating with the element to cause the actuation of the element to be eifected in accordance with the temperature of the translating apparatus.

17. A thermal relay for an electric circuit containing a translating apparatus comprising a thermally-responsive element heated in accordance with the circuit current, and magnetic means energized in accordance with the circuit current to develop heat, said means co-operating with the thermal element to cause said element to have an operating characteristic corresponding to the temperature characteristic of the apparatus.

18. A thermal protective device for an electric circuit comprising a thermal elementheated in accordance with the value of the circuit current and having one end thereof movable, and magnetic means secured to the thermal element and movable therewith, said means being energized in accordance with the circuit current for effecting movement of the free end of the thermal element.

19. A protective device for an electric circuit containing electric apparatus, comprising a thermally-responsive element heated in response to the thermal and the hysteretic effects of the current traversing the circuit and having the same heat characteristics as the apparatus.

20. A protective device for an electric circuit containing electric apparatus, comprising a thermally-responsive element heated in accordance with the current traversing the circuit and magnetic means for augmenting the actuating force of the thermal element by heat developed in the magnetic means to cause the total actuating force to bear a direct relation to the temperature of the apparatus.

21. A protective device for an electric circuit comprising a thermally-responsive element and means influenced by the magnetic flux' established by the circuit current for heating the thermal element, said means being intimately thermally related with the thermal element.

22. A protective device for an electric circuit comprising a thermally-responsive element and means intimately thermally associated with said element for heating the same in response to the hysteretic influence of the magnetic flux thereon.

In testimony whereof, I have hereunto subscribed my name this 27th day of May, 1920.

FREDERICK H. MILLER. 

